Project Summary Obesity among children and youth in the U.S. has become a serious public health problem. To date, there is still a large gap in our knowledge of the roles of family factors and child characteristics in the etiology of childhood obesity. A thorough understanding of the natural process of the problem and how the risks intersect and accumulate over the course of the child?s life is the key for effective intervention strategies. We propose to assess the longitudinal relationships of family factors (poverty, marital status/family structure, and maternal/paternal depression), child?s temperament, and child-rearing features (parenting styles, non-maternal child care) with the development of obesity and the transition/persistence of weight status over the different phases of childhood and adolescence. The National Institute of Child Health and Human Development (NICHD) Study of Early Child Care and Youth Development (SECCYD) has examined a national birth cohort of 1,364 subjects and have collected comprehensive information longitudinally, at frequent intervals from birth to adolescence (age 15), including parental and child characteristics, and standard measured body weight and height. Guided by the Life Course Theory and the Social Ecological Theory, the proposed study will determine if there are critical phases for risks and if there is an accumulation of risks across the child?s life in the development of childhood obesity. The study will explore the interplay between key family factors and child characteristics on childhood obesity risk, as well as examine the average/marginal effects of these individual variables on the development of obesity and the transition/persistence of weight status during childhood and adolescence. The specific aims are: 1) Aim 1: Assess the impact of family (poverty, marital status/family structure, maternal/paternal depression, parenting styles, non-maternal child care) and individual (child temperament) level characteristics on the development of obesity and the transition/persistence of weight status during childhood; 2) Explore the possible interplay of family factors and child?s temperament characteristics with child-rearing features (parenting styles, non-maternal child care) on the development of obesity and the transition/persistence of weight status during childhood. Mixed models, generalized estimating equations (GEE), and structural equation modeling (SEM) techniques will be used to analyze the data. This data set provides a unique opportunity to conduct a comprehensive data analysis with valid and accurate estimates of the dynamic associations of key family factors and child characteristics with obesity risk from childhood through adolescence. Therefore, our proposed study will significantly extend the current knowledge about the risk of and the pathways to obesity in childhood and adolescence. Findings from this study will help to identify key family contexts and child rearing practices for targeted interventions to promote health and reduce obesity.